In the prior art, many distance measurement systems exist, however, to the knowledge of Applicant, none of the existing systems have the flexibility of beamwidth shaping, ease of control, flexibility of reprogramming, low cost and minimization of components as are the case with the present invention.
In prior art systems known to Applicant, the ultrasonic transducers thereof are characterized by fixed beamwidth in both the horizontal and vertical planes which renders these systems inflexible for the many uses contemplated for the present invention. In another deficiency in the prior art, most distance measuring systems utilize a first transducer for transmitting and a second transducer for receiving. With such systems, it is quite possible that confusion will exist especially when the receiving transducer may be receiving signals which are not related to those which have previously been transmitted by the transmitting transducer. The following prior art references which are believed to be only generally related to the teachings of the present invention are known to Applicant:
Cudworth U.S. Pat. No. 3,226,673 discloses a device for indicating objects rearwardly of a vehicle which device includes a plurality of signal emitting transducers which may be mounted in transversely spaced relationship on the rear bumper of a vehicle. When an object is within a predetermined short distance of the rear of the vehicle an indication is given to the driver of the vehicle through the energization of an emergency or danger signalling circuit so that the driver knows that the vehicle is dangerously close to the object. This system utilizes separate transducers for the transmitting and receiving functions. This system is different from the present invention for several reasons. Firstly, the Cudworth system uses separate transmitting and receiving transducers whereas in the present invention, each transducer performs both transmitting and receiving functions sequentially. Thus, through the use of the present invention, more transmitter-receiver transducers may be placed in a given area. Furthermore, the Cudworth system uses no beam shaping techniques nor does it utilize time dependent gain control nor does it use microprocessor control and processing whereas the present invention includes each of these features.
Sato , et al. U.S. Pat. No. 3,778,823 discloses a system which senses an imminent collision so as to activate control means to blow up an air bag in a vehicle. The system operates through the use of microwaves and has separate transmitter and receiver antennas. The system measures both the position of an object and the speed by which the vehicle is approaching the object by the well known Doppler technique. The present invention is distinct from the teachings of Sato, et al. as utilizing ultrasound waves rather than microwaves, as using transducers which perform both the transmitting and receiving functions rather than separate transmitting and receiving transducers, and as utilizing beam-shaping techniques, time-dependent gain-control and microprocessor circuitry for control and processing, none of which are taught or suggested in Sato, et al.
Inoue U.S. Pat. No. 4,104,610 discloses an ultrasonic horn having a particularly shaped opening for beam shaping purposes. This device is different from the generally corresponding device in Applicant's system since Inoue discloses a horn whereas the present invention utilizes a slot which is significantly different therefrom. In one aspect, a horn in general cannot achieve as wide a beamwidth as can a slot and further, when size considerations are important, a transducer using a slot may be made much smaller than one which uses a horn.
Galvin, et al. U.S. Pat. No. 4,155,066 discloses an intrusion alarm system utilizing separate transmitting and receiving transducers having sensitivities which are reduced along the normal or boresight axis thereof and which are increased along axes angularly displaced from the boresight axis. This results in an energy pattern of reduced intensity along the boresight axis thereby reducing the intensity of standing waves which may occur thereat. This system is materially different from the present invention for many of the reasons set forth above and further because the Galvin, et al. device utilizes a cavity design to achieve a particular beam pattern whereas the present invention uses a slot to achieve a flat bell curve beam pattern.
Morgera U.S. Pat. No. 4,207,620 discloses an underwater mapping system utilizing a plurality of transducers which enable the measurement of a swath of terrain much wider than the beamwidth of the sonar pulses. This system is significantly different from the system of the present invention as failing to utilize beam shaping through the use of a slot and as failing to use a microprocessor for control and processing. The invention of Morgera only utilizes a microprocessor for beam steering and display purposes.
Duncan, et al. U.S. Pat. No. 4,240,152 discloses a device utilizing at least three transducers comprised of two transmitters and one receiver or one transmitter and two receivers which system may utilize a triangulation technique in order to find the location of an object. Of course, the present invention is different from the system as utilizing transducers which perform both the transmitting and receiving function. Furthermore, the present invention only measures the distance to the object whereas the system of Duncan, et al. utilizes a triangulation technique in order to find the location of the object, which is a complication for the purposes of the present invention. Further, other differences discussed above with regard to the other known prior art references also apply here.
Tournois U.S. Pat. No. 4,456,982 discloses a bidimensional imaging system which utilizes a transmitting array and a receiving array which system utilizes transmitted and received echoes. This system is believed to be related to Morgera, discussed above, and is discussed from the teachings of the present invention for the same reasons discussed with regard to Morgera.
Gelhard U.S. Pat. No. 4,500,977 discloses a motor vehicle mounted distance measuring device utilizing four different transducers and ultrasonic echo signals. Several differences exist between the teachings of Gelhard and those of the present invention. Firstly, Gelhard discloses a large number of different types of transducers which are used in his system whereas in the present invention, only a single transducer having the beam thereof shaped by a simple slot and controlled by the use of a time-gain scheme is used. Further, Gelhard teaches the use of a horn to narrow the beam in both directions whereas the present invention utilizes a slot. Thus, Gelhard is different from the present invention in the same manner as Inoue discussed above in this regard. Furthermore, the present invention utilizes the concepts of dynamic beam shaping, time-dependent gain-control and microprocessor control and processing none of which are taught or suggested by Gelhard.
Furthermore, Applicant is aware of U.S. Pat. Nos. 3,522,764; 3,523,275; 4,081,626; 4,085,297 and 4,199,246. Each of these patents discloses a transducer design per se and possibly the use of a particular transducer design in an application such as for a camera range finder. In the present invention, designs of transducers similar to those disclosed in some of these patents are utilized as a starting point and are extensively modified through the use of the slot device as set forth hereinabove for beam shaping purposes and thus, these references are believed to be of only general interest vis-a-vis the present invention.
The publication "A Prosthetic Aid for A Developing Blind Child" by Boys, et al. published in Ultrasonics Magazine, Jan., 1979, is believed to be only generally relevant to the teachings of the present invention as suggesting the concept of "blanking" during the measuring sequence. Otherwise, this publication is believed to be of only general interest concerning the teachings of the present invention.
Accordingly, a need has developed for an omnidirectional distance measurement system having the flexibility of beamwidth shaping, ease of control, flexibility of reprogramming low cost and a minimum of components. With these criteria in mind, the present invention was developed.